A sample collection medical worker in Mudanjiang takes off her protective clothing after becoming soaked in sweat due to the hot weather on June 1. Photo: Courtesy of medical staff in Mudanjiang

More than 650,000 people were tested for COVID-19 in Mudanjiang in seven days, and 19 asymptomatic infected people were detected, Wang Wenli, mayor of Mudanjiang in Northeast China's Heilongjiang Province, announced at a press conference on Monday afternoon, according to China Central Television.

"From June 1 to June 7, nucleic acid tests were completed on 658,772 people in the urban area of Mudanjiang within seven days. 19 asymptomatic infected persons were found, with a positive detection rate of 0.288/10,000," Wang said at the press conference.

Among the 19 asymptomatic infected people, 56.6 percent were male and 43.33 percent were female. The age ranged from 5 years old to 70 years old, Liu Yancheng, an official with the Health Commission of Heilongjiang Province said at the press conference.

Five of them are decoration workers. According to the nucleic acid and serological test results, these five decoration workers gather in a fixed place almost every day. They have behavior such as drinking tea, smoking and having dinner together, with an epidemiological correlation and certain infectivity.

The epidemic situation in Mudanjiang is of some concern because of imported cases at Suifenhe port. Mudanjiang has been the second city after Wuhan to conduct nucleic acid tests for all residents.

According to the official website of the Health Commission of Heilongjiang Province, no new confirmed cases or asymptomatic infected cases were reported from June 2.

As of Sunday, a total of 561 confirmed local cases have been reported, 548 cases have been cured and discharged from hospital, and 15 asymptomatic cases have been reported in Heilongjiang.

There were 525 patients in the fever clinic on Sunday. A total of 20,218 close contacts have been traced in the province, 20,055 have been released from medical observation, and 163 are still under medical observation.

According to the epidemic report on Sunday, there were no new confirmed imported cases or imported asymptomatic cases in Heilongjiang. A total of 386 confirmed imported cases have been cured and discharged from hospital.